CONCRETE A SHIT
Scientists have discovered the structure of the material which causes concrete in buildings to break down and crack
Shitty concrete buildings worldwide break down after a few decades because of the alkali-aggregate reaction, AAR.
1. Concrete's main component = cement
2. Cement contains alkali metals e.g. Na or K
3. Moisture (rain) + alkali metal -> alkaline solution
4. Concrete's 2nd main component = sand and gravel
5. Sand and gravel is composed of minerals like quartz and feldspar, which are silicates
6. Silicates + alkaline water -> alkali calcium silicate hydrates
7. Alkali calcium silicate hydrates absorb more water and expand
8. Cracks this maketh
Scientists have discovered that the alkali calcium silicate hydrates (ACSH) have a crystal, sheet-silicate structure - something which has never before been observed. It was found by taking diffraction pattern readings from wafer thin samples of AAR''d concrete with an x-ray beam 50x thinner than a human hair.
Boffins hope info about the structure of ACSH will help to provide a solution to cracking concrete to make it more durable, perhaps by adding organic material to relieve tension build-up.
Paul Scherrer Institute
Swiss Materials Science Lab Empa
JUST STOP BUILDING IN CONCRETE
MFW BEAUTIFUL UNIVERSITY COMPLEX/CAMPUS RUINED BY CONCRETE AND STEEL REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
I am sure many people on /sci/ have been at universities which have been victims of modern architecture.
Pic related. The modern part and the old part of my old university physics building.
>Concrete holds up pretty good desu. Much better than marble for example.
No, modern concrete can only last a couple hundred years or so in an even moderately wet environment. It doesn't just crack a bit and stop, it keeps cracking and breaking up until it's rubble.
Marble's fine in the right climate, without certain kinds of weather or pollution. The marble Parthenon stayed in good condition from 432 BC until the 17th century AD when it was badly damaged by a gunpowder explosion.
The Romans had concrete for much longer than we've had it, and without mechanized industry, they couldn't afford to treat the matter of crumbling structures lightly. They kept track of who had built what with materials from where, learned what lasted, and used it for their major projects they didn't want their grandsons to have to clean up and rebuild.
concrete is going to keep going for a long time. if anything, this will help chemists and engineers design better concrete
>No, modern concrete can only last a couple hundred years or so in an even moderately wet environment. It doesn't just crack a bit and stop, it keeps cracking and breaking up until it's rubble.
>Nope Roman concrete structures are basically perfect to this day. The problem is that our version is a poor imitation. A classic case of lost technology.
Another major cause of concrete deterioration is corrosion of steel rebar. As it rusts, it swells, breaking the concrete.
The new trend is toward basalt fiber rebar, like fiberglass, but made using selected basalt rather than silica with additives.
With concrete that's chemically more like the old Roman stuff, and rebar that doesn't rust, we may start building things that stand without maintenance for millennia.
It's something to take into account, but not always the whole picture. There are quite a few surviving major Roman concrete works. More than you could attribute to chance.
Or take furniture, for instance. Old furniture was put together with hide glue. You can fix it by melting the glue and pulling it apart, and the glue is flexible and holds well under repeated strain. Most new furniture is put together with PVA "carpenter's" glue, which is cheap and workable in the short term, but makes repairs very difficult and tends to eventually give way (applying more glue doesn't fix it, because the glue doesn't stick to itself -- you have to clean all the glue, which is harder than the wood, off both surfaces).
People work the bugs out of technologies that remain in use for hundreds of years. There are many things you could make a glue out of by simple recipies in the pre-modern era, but hide glue became the standard for furniture until modern synthetic chemistry mucked it up and seduced our carpenters with something cheaper.
Our rapidly advancing technology and increasing efficiency in manufacturing has definitely led to the production of a lot more disposable, short-lived junk.
I can't estimate how many concrete structures in rome were built in its 2000 year lifespan but i have an idea that if we were to see how much was built versus how much survived to this day, it wouldn't be that much more impressive than the amount of surviving ancient temples and pyramids
>>Now that we understand how stuff fails, we don't have to overbuild it, and can design it to last just enough cycles that people don't get annoyed buying more.
if you're the one whose so insistent on going back to the ancient lost art of roman concrete, we could just build better concrete structures by pouring a shit ton of concrete to make up for its absolutely pathetic tensile strength, which is what the romans probably relied on.
I don't think there are a lot of pyramids that were built and aren't there anymore. It's a big pile of stone. Even if the tunnels all collapse, it's still a big pile of stone.
The pyramids at Giza aren't anything like they were when they were new, though. The Great Pyramid, for instance, was smooth-sided, covered in marble, and capped with gold. Probably had a great big drawing on the side of the pharoah's anime waifu, too. Later generations stole the gold and marble.
STUFF DOESNT LAST FOREVER
SOME SHIT BREAKS DOWN AFTER A WHILE
BILLIONS OF PEOPLE IN OUTRAGE AS THEIR ROADWAYS AND HIG HRISE BUILDINGS UNDERGO YEARLY MAINTENANCE
MORE AT 11
IS CHANGING YOUR OIL ALL JUST A SCAM TO BUY MORE?
DO THE COMPANIES REALLY HAVE A SECRET FORMULA THAT NEVER BREAKS DOWN?
FIND OUT NEXT!
FRP wrapping, epoxy rebars, polyurethane coats, etc.
this concrete falling apart idea isn't news and engineers have found all sorts of ways to compensate for its flaws including all sorts of rebar types and rebar placements schemes, admixtures for desired material properties, microstructure, and air entrainment, different cement types for curing speed, methods for finishing, mix ratios for desired strength, numerous schemes listed above to resist harsh chemical attacks, pre-stressing, pre-cast, temperature monitoring for large thermal gradients, using steam to aid curing. Numerous ways of working and developing concrete. its an art and a science and its complicated as fuck. the romans could never dream of this shit. stuff falls apart only because nobody out there with the money cares about building 5000 year old monuments, and for those who actually care dont have the money to pay for it.
>the romans could never dream of this shit.
That doesn't mean they didn't have something better.
There's a fair number of things that we just haven't improved on, particularly when it comes to making stuff that lasts a long time. To make something last and be maintainable, you need experience more than you need theory.
If you want to take advantage of radically different technology, you need to step away from what might be centuries or even millennia of accumulated experience.
The romans had an incredibly poor understanding of structural mechanics.
Their method for making things stand up for a long time was row upon row of thick stone columns not just along the boundary of a structure but within it as well. Economically, of course, this was only available to the elite of the elite, and is not at all characteristic of any appreciable fraction of roman structures.
Anybody with the money today can build a stone structure better than the romans ever could by utilizing our understanding of structures - so, yes, this does in fact mean that the romans did NOT have something better.
If you want to compare our building methods to the roman's, you can't compare their absolute best to our low/economic-tier. That's clearly a poor comparison, but, sure, the best roman buildings ever made were in fact better than some of the worse buildings that we have made, but that's really not a useful or relevant fact.
>>if you're the one whose so insistent on going back to the ancient lost art of roman concrete
nope, just stating a fact about modern consumer product design. Buildings are designed to basically last forever though, a cheap weed wacker is designed to last a month. Cause we have failure theory now.
Its a gigantic free standing dome made of concrete, that we have no idea how to replicate, and uses much less material than we would think to be necessary today so I don't think the Romans relied on overcompensation like you suggest.
They used mortar in which they mixed in different minerals. pic related
It holds alot tighter than our mortar because the natural minerals interlock on a very small scale if pressurized.
other thing is, they used a method to fill in the hollow walls with concrete. while having heat hardened bricks on the outer layer.
will post pic too
this methods could still be valid today imho
the second and third one are of interest to us.
see how the wall has spikes on the inside for increased stability.
Roman aqueducts still going strong
>trusting the internet jew
That decay is why Los Angeles is getting rid of an iconic bridge. The engineers found out that decay has compromised the structural integrity of the bridge, and it will collapse in the event of a major earthquake. There is a new mix of cement that fixes this error. I believe the Chinese are the ones who used this method.
>>If you want to compare our building methods to the roman's, you can't compare their absolute best to our low/economic-tier.
Like half of the Stirling Prize winners, apparently the best buildings built, have needed structural repair.
Modern architects would fail dismally if they ever tried to build a sturdy classical building using time-tested classical methods. It would be far too hard for them. Let alone decorating it correctly.
Goddamn those structures have a strange sense of beauty and coherence to them.
Not only have humans become garbage at architectural aesthetics, engineering goals and processes have shifted to a point where it's not just viable, but ACCEPTABLE to build acre after acre of pavement fields to serve ugly as fuck buildings that fall apart in ~30 years.
“Today’s scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality. ”
― Nikola Tesla
More or less echoes what I've felt more and more through my life. And that was probably !100 years ago.
People are quick to attack when aspects of science are compared to typical religious thought, but it's always been the case to an extent, and is growing to be the norm for "the public". I wonder where it all goes. Quantum mechanics is by far the worst of it. I hope some experimentalist finds a means to reconcile some of this mess.
I will now tell you something I discovered yesterday but has been around for long.
Conways Game of Life or Cellular Automata
This algorithm can create patterns in infinite space.
with rules only set at the beginning. no manual interference between beginning and end.
this needs considerably more processing power, but the result is always real.
If we not already are, I think we will use this method to programm smart materials, which have the ability to arrange and rearrange themselves.
interesting times ahead imho
You mean shitty concrete is shit.
It is sad that the more we know the more we use the knowledge to take short cuts. I have studied material engineering and worked part time in construction. I am constantly shocked at how poorly we build things on every level. What is more many good solutions are stuck in development hell or cost too much, often only because the new market is not yet big enough to get economies of scale.
Thing is every project needs a whole design approach which includes more then the cheapest or easiest way. But a quick way to grab markets used by many materials suppliers is price, so low everyone uses it even if it is not the best. Or easy of install, so easy why get a professional when I can do it myself. The result is often devastation but by that time such practices are often codified for safety to the point better ideas can not be used.
It was better bonding chemistry in concrete, we just started relying on the chemistry without thinking about the rest of the design. I mean we even have fast dry concrete that says "just add water" on the bag. You think a skilled concrete worker from the 1930s would even think about using this stuff? Don't get me wrong that new tech is useful and can make things better, just not for every project and more so if used by a typical contractor who doesn't have a decent skill level.
God forbid that anyone would want to cramp up LA with some piece of shit that's going to be stuck there for a thousand years. Imagine if the asshole that would curse LA traffic with a fucking 2 lane I-10 for the next 500 years.
>Anybody with the money today can build a stone structure better than the romans ever could by utilizing our understanding of structures - so, yes, this does in fact mean that the romans did NOT have something better.
Pay some attention to the rest of the thread. We're not talking about stone, Romans made lots of *concrete* that is still around after about two thousand years.
How they made it and why it lasts better than our imitations, despite all our knowledge of chemistry, has been a subject of active research for basically as long as we've had chemistry.
>you can't compare their absolute best to our low/economic-tier.
Plenty of stuff that's not low-tier is crumbling. Besides, once you have a decent building, you don't want it to depreciate and need repair. A big part of the value of a building is being able to resell it.
The Romans were long-term thinkers. They venerated and sometimes deified their ancestors, so they wanted their descendants to look back on them as great men, and be surrounded by beautiful and practical things which survived from their time.
>How they made it and why it lasts better than our imitations, despite all our knowledge of chemistry, has been a subject of active research for basically as long as we've had chemistry.
It is not some secret.
They used volcanic ash that formed strätlingite crystals fibers that strengthened it.
They used a lower water content and worked it by hand to increase the density, with some reports suggesting they pounded it into form like moist sand.
They were more selective with their particles agents. The sand used has sharp and jagged surfaces for more surface bonding then the smooth sand we use, it was also smaller then our modern gravel agents. Even their bulk filling agents were strong high fired brick pieces rather then rocks left over from industrial blasting, as blasting can leaves a large amount of cracks filler rocks.
They also avoided sharp geometry that creates high stress points and would use tailored bricks to work with the concrete for better bonding and as an outer coatings for addition moisture protection on non-cosmetic parts.
These things are not that complicated, in fact we can enhance them with our better understanding. That said this makes installation very labor intensive, but they had slaves trained to do it with good skills.
>It is not some secret.
>some reports suggesting
Yeah, sounds really completely understood.
>They used volcanic ash that formed strätlingite crystals fibers that strengthened it.
That was discovered when? About a year ago? By using a fucking particle accelerator?
> How they made it despite all of our knowledge.
>Active area of research.
>implying that there's a huge research effort ongoing to study ancient mysticism bullshit and holy grail of magic meme materials
> Implying that the people who care are more than a dozen academics and pop- sci crowds that would waste someone else's money on memes material structures like solar powered graphene bridges or vertical cities made of space age pop-sci materials
>implying that there's a huge research effort ongoing to study ancient mysticism bullshit and holy grail of magic meme materials
Nobody said anything about a "huge" research effort, mysticism or magic.
The Romans had the advantage of time, having had cultural continuity over more than a millennium, and the motivation of a non-mechanized, low-energy society that knew it made progress by building things that remained useful for future generations. They didn't have to understand what was happening, they just had to keep track of what worked.
And holy shit, you're just breaking down into a tantrum here.
That's poor reading comprehension on your part and you are prone to confusion. Are you the same person who's who thinks concrete is bad but wants ancient magical concrete at the same time?
After you spend 3 weeks as a gofer dropping off and submitting papers for a master architect to get an alteration in a stone threshold for a patio door you realize how broken the code is.
Yes, the client wanted a seamless look which the standard designs under the ICC did not explicitly support. However I can show that the proposed design solution he made had a full foot reduction in the span that didn't even have an active load and had nearly a full inch more of float space to absorb any stress, including earthquake conditions which is largely irrelevant at this location. Overall this design had a 40% increase in life expectancy using the model provide by the regulating authorities.
You know what they said? They said it was unsafe even when their models showed it to be better in every single respect, including safety. Even the tip hazard profile was below there negligible tolerance yet trip hazard was number 4 on their long list of reasons this threshold design was unsafe. Number 73 cited the untested flammability of material in question, you would not believe how much time I wasted proving to them slate does not pose a fire risk. Apparently flammability testing data for walls and floors made of slate can not be used for threshold application. As that is a different part of the house and I could not find any prior test data for that specific application.
After fighting over this single detail for 3 weeks the company ended up underwriting a $40,000 insurance plan specifically to cover the home owner should any damages be caused by this threshold we designed, in addition to the normal insurance and liability we take on all jobs. That cost us and the home owner time and money, but we had to do it or we could not build this threshold because of code.
I was so mad I also personally underwrote a $100 policy "... should the slate threshold spontaneously bust into flames or catch fire ..." just to force the regulator sign, seal and separately mail 10 copies.
>That's poor reading comprehension
No. Your statements were parsed and meaning extracted properly. If anything it's "poorly" reading between the lines, which has less to do with comprehension and more to do with what data set you have to interpolate / extrapolate from.
> Are you the same person who's who thinks concrete is bad
>but wants ancient magical concrete at the same time?
Ancient magical concrete would be neat.
>the level of awe and worship of roman concrete deserves such mockery.
You're one of these guys who protects his ego by imagining ridiculous things about other people constantly, aren't you?
Don't worry, deep down, you really are much better, smarter, and more rational than everyone else. Never let reality intrude on that belief.
Let see what was said here in this thread
>concrete is finally going to die
>we don't know how romans made such long lasting concrete. Modern society is technically incompetent.
Not completely true. We can make stuff last long if we really wanted, and roman concrete is overrated
>Its up there for you to read. As of now, everthing I said still stands.
...and this is how you come away from arguments feeling like you won: act like an idiot, and when people stop talking to you, declare victory.
The suggested reporting is from the lack of detailed documentation surviving since ancient the construction of ancient Rome on this topic.
Now we can prove most of what is said such as the the water content was lower during construction and that the packing is much tighter.
But when it comes to the process used to achieve the tight packing is an educated assumption only backed by similar result of more recent testing of suspected methods. Not by direct documentation of the workers so it can not be said to be certain. We can only say that the suspected methods tested yielded very similar results to artifacts found using tools and techniques that were likely available at that time period.
The ash additive has been know for a long time as it was documented, included which volcano was favored for its superior proprieties. The Washington Post had an article about the crystals in 2014, but I remember hearing about it at a concrete conference a more than a year before that. There was rumors of it as far back as 2008 and likely earlier, but nobody seemed to be pushing the research as carbon footprint reduction was the big deal then. Oddly enough these discoveries offer ways to reduce the carbon foot prints.
Also it is not a particle accelerator it is an x-ray diffractometer or just XRD for short. Well I supposes you can call those photons particles which are accelerated. But in the material testing labs I have visited that term is mostly for accelerated atoms and electrons. Sometimes protons and neutrons, but most of the labs don't have that equipment. We tend to treat photons and phonons as waves mostly in this disciple.
>>I mean then explain why we cannot recreate the Pantheon as a freestanding concrete dome
Be a little bit more specific. The glib answer would lie in finding a modern day client interested in a replication of the Pantheon. I would also have to question if there are any widely accepted modern building codes that allow something like the pantheon to be built without any reinforcement.
>By using a fucking particle accelerator?
Yes. X-ray diffraction has been the gold standard for analysing crystal structures since forever (we worked out the structure of DNA with X-ray diffraction), and the best way to generate really intense X-ray beams is with a synchrotron.
"a fucking particle accelerator" has been one of the standard tools for materials science for quite a while.